An interdisciplinary study at the Australian National University (ANU) has discovered evidence that the Portland Vase, a 1st century A.D. Roman cameo glass of extraordinary beauty that has captured the imagination of the artists and antiquarians for half a millennium, may have been manufactured completely differently than scholars have thought up until now.

Specifically, by using a combination of computed tomography and mathematical analysis the researchers have shown that Roman cameo glass was not made by blowing, but by a different process known as “pate de verre”.

While glass-blowing involves basically inflating a balloon of molten glass by pushing air into it through a tube, pate de verre is a form of casting. Finely crushed glass particles are mixed into a paste with a binding material (and colours), which is then put on the inner surface of a mould and then fired.

Research on Roman cameo glass fragments led by Richard Whitely of the Australian National University (ANU) in Canberra focussed on studying the fine structure of air bubbles trapped between blue and white layers. The collaboration between the university’s schools of art and design, classics, and physics and engineering revealed evidence that the glass could not possibly have been produced by blowing.

“We saw a bubble configuration within the glass that results from a pressing and turning motion,” says Whiteley. “I believe that cold granulated glass has been packed into a mould and then a blob of molten blue glass introduced and pressed against mould heating the white granules from behind. You just would not get a bubble that size and flat-shaped from blowing.”

He knows whereof he speaks, because Whiteley is an experienced glass artist in his own right. His first-hand knowledge of how glass works was supported by Tim Senden from the school of physics and engineering who analyzed the data from the scans. Senden created mathematical models of the glass bubbles and found they were not compatible with bubble patterns created during the process of blowing glass.

The Portland Vase has been confounding and enchanting people if not since it was made between 1 and 25 A.D., then at least since its rediscovery in the Renaissance. It is believed to have been found in a tomb just southeast of the ancient Servian walls that still marked the official boundary between the old city (where bodies could not be buried) and the outskirts (where they could). Known as the Monte del Grano (the hill of grain), the grave purportedly contained a large marble sarcophagus thought to be the final resting place of Emperor Severus Alexander (r. 222-235 A.D.) and his mother Julia Mamaea. The imperial attribution proved to be groundless, but the legend stayed attached to the vase, which was found inside the sarcophagus and because of its exceptional quality was assumed to have been used to contain the ashes of the emperor, for centuries.

The discovery was not documented at the time so a lot of this story is nebulous in its details. It was well-established as the background of the vase by the 18th century, but the first known recorded reference to the Portland Vase was a comment by Nicolas-Claude Fabri de Peiresc who saw the artifact in the winter of 1600-1 in the collection of Cardinal del Monte. Peiresc was riveted by it as were his friends Peter Paul Rubens and antiquary Cassiano dal Pozzo whose “Paper Museum” (a collection of more than 7,000 paintings, watercolors and sketches of antiquities, botany, zoology, architecture and more) included multiple drawings of the vase. The three of them wrote to each other about it often, discussing its aesthetic attributes, imagery, original shape and date of manufacture.

As secretary to Cardinal Francesco Barberini, dal Pozza had front-row seats to the cameo glass vase. Cardinal Del Monte died in 1626 and the vase was acquired by the Cardinal’s brother Antonio, both nephews of Pope Urban VIII. That’s where the vase got its next name: the Barberini Vase. The family was the most powerful in Rome at that time and had patronage ties to artists all over Italy. Word of the rare beauty of the vase spread far and wide in the artistic community, and by the end of the century it was considered a must-see for antiquarians, artists and well-bred amateurs who would later become known as Grand Tourists.

Not that anybody had any accurate idea of where it came from or even what it was made out of at this point. Late 17th century sources from encyclopedist Bernard de Montfaucon to Giovanni Battista Piranesi, meticulous engraver of antiquities and fantasy prison landscapes, repeated the story that the vase had been found in the Monte del Grano tomb in the sarcophagus of Severus Alexander. Piranesi engraved the tomb, sarcophagus and vase in his characteristic high detail, but he hadn’t seen them together as the original context was long since scattered. Montfaucon and Piranesi both mistakenly thought the vase was made of sardonyx agate, and they weren’t the only ones to make that mistake.

Sir William Hamilton bought the vase from Scottish antiquities dealer James Byres in 1782 who had bought it from the debt-ridden Donna Cordelia Barberini-Colonna in 1780. In 1784, the vase ceased to be a Barberini and found a new home (and a new name) with the Duchess of Portland. She died the next year and her great collection was sold at a multi-day auction. The buyer of the vase kept things in the family, however, because he was the Duchess’ son, the 3rd Duke of Portland. A year after the sale, Josiah Wedgwood got permission to borrow the vase to make copies in jasperware. His versions were huge commercial hits and geometrically expanded the fame of the original vase.

The Portland Vase darkened the doorway of the British Museum in 1810 when the 4th Duke of Portland loaned it to the institution for safe-keeping, but alas, there is no safety to be found in a world full of crazy people. On February 7th, 1845, a paranoid alcoholic on a bender picked up one of the carved stones on display in the gallery and smashed the Portland Vase and its vitrine to bits. It wound up in 37 pieces but was puzzled back together by restorer John Doubleday within a year. It was finally bought by and entered the permanent collection of the British Museum in 1945.

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Indeed, Emperor Severus Alexander and his mother Julia Mamaea -i.e. under normal circumstances, you never know- NEVER EVER would have themselves depicted (cf. Plate XXXIII) on their sarcophagus as an Etruscan couple would have on theirs a few centuries earlier

It would have made perfect sense for the original artist to have tried to devise a method whereby the enormous effort required to create the figures and scenes could be duplicated with less skill or at least effort. Time was money then as well. Was an original created as a “one-off” then used to create a female mold by the same or another artist? There are many Roman glass techniques that have not been rediscovered. The idea of using a paste of white glass put into the “female” impressions of a clay(?) mold would make perfect sense. Presumably this would require a two piece mold, and therefore no “overhangs” in the profiles of the raised scenes that would prevent the final piece being removed from the mold; but perhaps the artists found a way to dissolve the clay mold?? This would allow the use of more complex profiles which a halved or even quartered mold would not. Such shapes would have required much handwork on the molds themselves, but clay is much easier to work than glass!